Long DNS Time Analysis
Issue Description
DNS resolution time is longer than expected.
Normal DNS Time
| Quality | DNS Time |
|---|---|
| Good | <50ms |
| Normal | 50-200ms |
| Poor | >200ms |
Possible Causes
DNS Server Issues
- DNS server overload
- DNS server misconfiguration
- DNS server distance
- DNS cache misses
Network Issues
- Network congestion
- High latency to DNS server
- Packet loss
- Routing issues
Domain Issues
- Complex DNS chain
- Multiple CNAME records
- DNS record propagation
- Authoritative server issues
Client Issues
- Local DNS cache expired
- DNS client misconfiguration
- Firewall blocking DNS
- ISP DNS problems
Investigation Steps
-
Check DNS Path
- Run nslookup
- Check DNS resolution chain
- Identify slow step
- Compare DNS servers
-
Analyze Patterns
- Check affected regions
- Check affected ISPs
- Review timing patterns
- Correlate with changes
-
DNS Diagnostics
- Test different DNS servers
- Check DNS cache status
- Verify DNS records
- Measure each step
-
Network Analysis
- Check latency to DNS servers
- Review packet loss
- Analyze routing
- Check firewall rules
Resolution
Quick Fixes
- Use public DNS (8.8.8.8, 1.1.1.1)
- Increase DNS cache TTL
- Reduce CNAME chain
- Fix DNS configuration
Long-term Solutions
- Deploy local DNS resolvers
- Implement DNS caching
- Optimize DNS records
- Use DNS preload
Monitoring
- Set up DNS time alerts
- Monitor DNS trends
- Track DNS provider performance
- Regular DNS audits
Prevention
- Regular DNS performance checks
- Document DNS changes
- Use reliable DNS providers
- Implement DNS redundancy